It is often desired to provide tires for vehicles that can be operated in a deflated condition for a suitable distance at a desired speed. The purposes have been varied, ranging from a desire to eliminate a vehicular spare tire so that its occupied space could be more efficiently used for other purposes and, also, a desire to enable a vehicle to remain operable even with a punctured pneumatic tire for a suitable time or distance whether or not a spare tire is available.
In some instances, such objectives have been proposed to be accomplished by positioning a run-flat device within the tire-wheel cavity to prevent the tire, upon an appreciable loss of internal inflation pressure, from going completely flat. Such run-flat devices can be substantially rigid in nature and prevent a total collapse of the tire by supporting the tire's inner surface in its crown region in proximity of the ground contacting portion. In such condition, the tire is prevented from going flat against its rim and, moreover, substantially retains its inflated circumferential shape and enables its vehicle to continue its travel over a more reasonable distance.
U.S. Pat. No. 5,787,950 discloses a rim, supporting ring and assembly intended for mounting a tire having at least two beads. The rolling assembly is intended for use in the event of travelling when the tire inflation pressure drops abnormally with respect to the nominal pressure of use and when the inflation pressure may even be zero. Such assembly is known throughout the industry as the PAX design and which has been commercialized by Michelin. The supporting ring is made of vulcanized rubber that has been reinforced by wires or cables arranged circumferentially to within about 2°. In order to achieve the high degree of stiffness in the vulcanized rubber, large amounts of filler are used.
However, it is considered necessary to provide lubricity at the interface between the supporting ring and a collapsing tire's inner surface in order to retard or reduce an attendant potential frictional, destructive heat build up at the tire's inner surface. Accordingly, it is often desired to provide a lubricant for such interface.